Intravascular Pulmonary Artery Tumour Mimicking Nodal Recurrence and Inadvertently Sampled by EBUS-TBNA: A Case Report.

Pulmonary artery tumours are rare and may mimic thromboembolism or nodal recurrence on imaging. We report a woman in her 70s with a history of resected stage IB lung adenocarcinoma who underwent endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) for a mediastinal lesion suspected to be nodal recurrence. During the second needle pass, synchronous lesion movement and increased bleeding were observed. Histopathology revealed high-grade sarcomatous cells with weak focal thyroid transcription factor-1 (TTF-1) positivity and h-caldesmon/myogenin expression, unlike the primary adenocarcinoma. Subsequent imaging confirmed that the lesion was intravascular within the pulmonary artery. EBUS-TBNA may inadvertently sample a pulmonary artery tumour when it mimics nodal recurrence during post-resection surveillance. Synchronous lesion movement and unexpected bleeding may indicate pulmonary artery puncture. Sarcomatoid transformation of adenocarcinoma and primary intimal sarcoma remained competing diagnoses because tissue was insufficient for molecular confirmation.